Heretofore ink jet print heads of various types have been produced, including both non-air-assisted and air- assisted drop-on-demand and continuous ink jet print heads. As exemplified by the ink jet print heads of U.S. Pat. No. 4,685,185 of Boso et al. and U.S. Pat. No. 4,728,969 of Le et al., ink jet print heads frequently are formed of plural metal laminates or components which are secured together.
These ink jet print heads typically have ink supply conduits through the laminates and the laminates normally define one or more compartments for receiving ink. In addition, air-assisted ink jet print heads include air flow passageways through the laminates. Also, as shown by the aforementioned Le et al. patent, some ink jet print heads may have purging passageways. In addition, these ink jet print heads typically have ink droplet ejection plates with minute ink orifice outlets, for example, thirty to eighty microns in diameter, through which ink drops are ejected. In air-assisted ink jet print heads, these ink drops typically pass through an air chamber and exit from an external orifice in an air chamber plate under the assist of air flowing from the air chamber.
During manufacture, the various ink jet print head orifices and passageways must not be occluded. A more stringent requirement for array jet print heads is that the passageways must not be even partially occluded because if they are, the various jets can have different performance characteristics. In air-assisted ink jets, it is also important for the ink-drop-forming orifice outlet and external orifice to be accurately aligned, typically concentric with one another to within three microns, for accurate ink drop ejection. In addition, bending, deformation or distortion of the ink drop ejection plate, and of the air chamber plate in the case of air-assisted ink jet print heads, can interfere with the accurate directional ejection of ink drops from the ink ]et print head. Also, performance of ink jet print head arrays is adversely affected by rotation of the ejection plate relative to other components of the ink et print head and relative to the air chamber plate in the case of air-assisted ink jet print heads. Also, relative rotation of plates forming an ink jet print head during manufacture can result in the misalignment of orifices and passageways in the ink jet print head.
In a common ink jet print head manufacturing technique for air-assisted ink jets, attachment of various laminates forming the ink jet print head is performed under a microscope with a worker aligning the various orifices as the ink jet print head is assembled. It has proven difficult to maintain the various ink jet print head components in alignment as these components are attached. Therefore, the yield of satisfactory ink jet print heads from such a technique is in need of improvement.
The Boso et al. patent attempts to overcome this alignment problem by forming a number of the apertures, for example an ink orifice outlet and an orifice between a horn compartment and an ink compartment, after plates or laminates containing these orifices are mounted in place. In addition, in the case of air-assisted ink jet print heads, Boso et al. optionally forms the external orifice prior to mounting the air chamber plate in position.
At Column 8, Lines 46-63, the Boso et al. patent discloses that steps for attaching the various ink jet print head components can comprise a brazing step. Nickel-gold alloy braze rings are mentioned. During melting of these braze rings, Boso, et al. recites that there is some diffusion of the gold and nickel into adjacent stainless steel components of the ink jet print head. This diffusion changes the percentage composition of the alloy and raises its re-melting temperature. Consequently, during a subsequent brazing operation, previously brazed joints do not melt because the temperatures at the joint are below the re-melting temperature. Finally, Boso et al. mentions that a spacer utilized in the described ink jet print head can be coated with an electroformed or electroplated layer of silver braze material.
The braze rings used by Boso et al. for each layer were from 25 to 75 microns or more in thickness. In addition, the Boso et al. brazing steps were accomplished with a pressure of approximately eighty pounds per square inch being applied in a direction normal to the plane of the various ink jet print head components during the brazing operations. Ink jet print heads of the Boso et al. construction have been sold for more than one year.
The Boso et al. approach is relatively time consuming and expensive because of the amount of brazing material used and because of the need to form apertures following the mounting of the various ink jet print head components. In Boso et al., if the ink jet orifice were formed prior to brazing, the braze material could easily accumulate in and occlude these tiny apertures.
Therefore, a need exists for an improved method of manufacturing ink jet print heads which is directed toward overcoming these and other disadvantages of prior art approaches.